Interaction Of The Ruminal Cellulose-degrading Bacteria And Fungi With Fiber Degradation

Two strains of ruminal anaerobic fungi and three strains of cellulolytic bacteria were cultured sole, mixed or sequently to study their relationship in cellulose degradation. Effect of different carbon sources on the relationship was also studied. The 13C-labeled cellulose was added as substrate to accurately track the way of fiber degradation and evaluate the contribution of ruminal anaerobic fongi and bacteria on the fiber degradation and their relationships.In our study, Clostridium berjerinckii, Enterococcus faecium, Ruminococcus albus, Neocallimastix spp and Cyllamyces spp showed normal fiber degradation characteristics and growth rate. When Clostridium berjerinckii were co-cultured with Enterococcus faecium or Neocallimastix spp, the fiber degradation ability was increased. However, no interreaction was found between Clostridium berjerinckii and Cyllamyces spp. The inhibitory effect was found when Clostridium berjerinckii were co-cultured with Ruminococcus albus. Co-culture of Ruminococcus albus with Enterococcus faecium, Neocallimastix spp or Cyllamyces spp reduced fiber degradation. Co-culture of Enterococcus faecium and Neocallimastix spp increased fiber degradation. No effect was found when Cyllamyces spp were co-cultured with Enterococcus faecium or Neocallimastix spp. Sequential culture of Clostridium berjerinckii, Enterococcus faecium and Ruminococcus albus showed their interaction on cellulose digestion. If fiber degradation increased, the reason was anaerobic fongi promoted the growth of cellulolytic bacteria. If fermentation was inhibited, the reason was fiber degrading bacteria inhibited growth of anaerobic fungi. The promoted fermentation was mainly caused by the previous bacterial metabolites when bacteria were sequential cultured. While the increased degradation rate of dry matter was largely the result of increased fiber binding sites. The reduced gas production was caused by the metabolite and fiber binding sites of bacteria. That decreased concentrations of NH3-N, TVFA and enzyme activity were because of the fiber binding sites. Among three different substrates (cellulose to starch ratio were 10:0, 5:5,7:3.), the ratio of 7:3 induced the most stable concentration of microbe protein, VFA, NH3-N, and degradation rate. This suggested the ratio of 7:3 was beneficial to the growth of microbes and substrate fermentation. The main fermentation product of 13C-cellulose was VFA when the rumen cellulose bacteria and fungi were single cultured. However, when they were mixed cultured, 13C content in VFA decreased. We explored the relationship between anaerobic fungi and fiber degrading bacteria in fiber degradation, the results had important significance to improve the utilization of low-quality roughage.